Silicon is a material capable of occluding lithium by alloying lithium and has recently become attractive as a material for obtaining a high energy density battery because of its high theoretical capacity. However, there is a problem that cycle characteristics of an electrode including silicon as an active material are worse than that of a carbon material such as graphite. One of the causes for this is believed to be that expansion and shrinkage of the silicon active material during charge and discharge are large and create stress. The active material is pulverized and separates from the current collector and deteriorates current collectability.
It has been found that gaps are formed in a direction of thickness of a thin film of an amorphous silicon deposited on a current collector such as a copper foil by charge and discharge and the thin film is divided into columns by the gaps and such thin film provides excellent cycle characteristics (International Publication No. WO 01/31720.)
However, there have not been any proposals relating to conditions of charging and discharging for improving the cycle characteristics of an electrode.